1. Field of the Invention
The present invention relates to a high frequency wave glass antenna for an automobile, which is appropriate to receive a digital terrestrial television broadcast in Japan (471 to 771 MHz), a UHF band analog television broadcast (473 to 767 MHz) or a US digital television broadcast (698 to 806 MHz).
2. Discussion of Background
There has been proposed a high frequency wave glass antenna for an automobile, which is shown in FIG. 2 and which is suited to a VHF-High band for an analog television broadcast (see, e.g., JP-A-2005-101809, page 1 and FIG. 1). In this prior art, a rear window glass sheet 33 includes a defogger, which comprises a bus bar 35 and a bus bar 36 connected by a plurality of heating wires 37. The plural heating wires 37 have a short-circuit wire 15 formed at central portions thereof in a left-to-right direction thereof. The rear window glass sheet 33 includes a branch heating wires 37a in the vicinity of a central portion in the left-to-right direction in a blank region above the defogger, the branch heating wires being branching off of the heating wire disposed at the highest position. The rear window glass sheet has a region 31 on a right portion of the blank region for provision of an antenna conductor (not shown). The rear window glass sheet also has another region 32 on a left portion of the blank region for provision of another antenna conductor (not shown). In FIG. 2, reference symbol 34 designates the vehicle opening edge for a window.
The above-mentioned structure enables the prior art system to receive a VHF-High band for an analog television broadcast. However, when the prior art system is applied to receive a digital terrestrial television broadcast in Japan or a US digital television broadcast, heating wires 37 in an upper portion of the defogger mainly have an adverse effect on the antenna conductors, causing the problem of having an insufficient antenna gain.
It is an object of the present invention to provide a high frequency wave glass antenna for an automobile, which is capable of solving the above-mentioned problem of the prior art.
The invention provides a high frequency wave glass antenna for an automobile, comprising a plurality of heating wires and a plurality of bus bars for feeding the heating wires, disposed in or on an automobile rear window glass sheet, the heating wires and the bus bars forming a defogger, the heating wires extending in a horizontal direction, a substantially horizontal direction, a direction along an upper edge of the rear window glass sheet or a direction along a lower edge of the rear window glass sheet; and an antenna conductor disposed in an upper blank region of the rear window glass sheet except for a defogger region;
wherein it is assumed that there is a line, which passes through the center of the antenna conductor or the center of gravity thereof, and which extends parallel to the heating wire at the highest position, is called an imaginary parallel line; and
an island-like conductor containing a linear conductor is disposed at one or more locations in a region of the rear window glass sheet between the imaginary parallel line and the heating wire at the highest position as viewed three-dimensionally.
The present invention also provides a high frequency wave glass antenna for an automobile, comprising a plurality of heating wires and a plurality of bus bars for feeding the heating wires, disposed in or on an automobile rear window glass sheet, the heating wires and the bus bars forming a defogger, the heating wires extending in a horizontal direction, a substantially horizontal direction, a direction along an upper edge of the rear window glass sheet or a direction along a lower edge of the rear window glass sheet; and an antenna conductor disposed in an upper blank region of the rear window glass sheet except for a defogger region;
wherein an island-like conductor containing a linear conductor is disposed at one or more locations in a blank space without having a bus bar or a heating wire, the blank space being in the defogger region.
The present invention also provides a high frequency wave glass antenna for an automobile, comprising a plurality of heating wires and a plurality of bus bars for feeding the heating wires, disposed in or on an automobile rear window glass sheet, the heating wires and the bus bars forming a defogger, the heating wires extending in a horizontal direction, a substantially horizontal direction, a direction along an upper edge of the rear window glass sheet or a direction along a lower edge of the rear window glass sheet; a first antenna conductor disposed in a right portion of an upper blank region of the rear window glass sheet except for a defogger region; and a second antenna conductor disposed in a left portion of the upper blank region of the rear window glass sheet except for the defogger region;
wherein when it is assumed that there is a straight line, which extends parallel to a plane parallel to a longitudinal direction of the automobile and the vertical direction, which passes through the center of the first antenna conductor in a left-to-right direction thereof or the center of gravity thereof, and which passes through at least one of the heating wires, this straight line is called a first antenna-side imaginary straight line;
wherein when it is assumed that there is a straight line, which extends parallel to the plane parallel to the longitudinal direction of the automobile and the vertical direction, which passes through the center of the second antenna conductor in a left-to-right direction thereof or the center of gravity thereof, and which passes through at least one of the heating wires, this straight line is called a second antenna-side imaginary straight line;
wherein when a heating wire, which starts with a top portion of a first bus bar or a portion of the first bus bar in the vicinity of the top portion, which extends toward the center of the rear window glass sheet in a left-to-right direction thereof, and which reaches and is connected to a top portion of the second bus bar or a portion of a second bus bar in the vicinity of the top portion, is called a highest original heating wire;
the highest original heating wire has at least one branch heating wire branched off thereof on the way to the center of the rear window glass sheet in the left-to-right direction after the highest original heating wire intersects or crosses over or under the first antenna-side imaginary straight line,
after the branch heating wire branches off of the highest original heating wire and extends further, the branch heating wire bends so as to extend parallel or substantially parallel to the highest original heating wire and extend toward the center of the rear glass window sheet in the left-to-right direction, and bends to join and be connected to the highest original heating wire on the way to a location where the highest original heating wire intersects or crosses over or under the second antenna-side imaginary straight line;
wherein the first antenna conductor and the highest original heating wire have one or plural island-like conductors disposed therebetween;
wherein the second antenna conductor and the highest original heating wire have one or plural island-like conductors disposed therebetween;
wherein the highest original heating wire and the heating wire just under the highest original heating wire have one or plural island-like conductors disposed therebetween under the first antenna conductor;
wherein the highest original heating wire and the heating wire just under the highest original heating wire have one or plural island-like conductors disposed therebetween under the second antenna conductor; and
wherein each of the island-like conductors contains a linear conductor.
By adopting the above-mentioned structure in accordance with the present invention, it is possible not only to minimize the adverse effect on an antenna conductor by a heating wire but also to improve the antenna gain on reception of a digital terrestrial television broadcast in Japan or a US digital television broadcast. It is also possible to minimize the possibility that the sight through the rear window glass sheet, in particular, the sight through the defogger region, and the appearance of the defogger region are damaged.